21291249 has 16 divisors (see below), whose sum is σ = 33563520. Its totient is φ = 11746560.

The previous prime is 21291247. The next prime is 21291269. The reversal of 21291249 is 94219212.

It is a happy number.

It is not a de Polignac number, because 21291249 - 2¹ = 21291247 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21291247) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16872 + ... + 18089.

It is an arithmetic number, because the mean of its divisors is an integer number (2097720).

Almost surely, 2^21291249 is an apocalyptic number.

21291249 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21291249 is a deficient number, since it is larger than the sum of its proper divisors (12272271).

21291249 is a wasteful number, since it uses less digits than its factorization.

21291249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35000.

The product of its digits is 2592, while the sum is 30.

The square root of 21291249 is about 4614.2441417853. The cubic root of 21291249 is about 277.1620168925.

The spelling of 21291249 in words is "twenty-one million, two hundred ninety-one thousand, two hundred forty-nine".